The present invention relates to a poppet valve which is directly used for supplying working fluid such as reaction gas or the like in physical and/or chemical machines or the like or which is used for pressure reduction of a vacuum chamber using such reaction gas or the like. More specifically, the present invention relates to a poppet valve with a heater that is constituted so as to prevent product from the working fluid from adhering to a valve member or the like by a heater.
In a manufacturing apparatus for semiconductors, for example, reaction gas with a high temperature is used for such a chemical processing as an etching which is transferred in a vacuum chamber, and a poppet valve is used for supplying the reaction gas or reducing pressure in the vacuum chamber. However, when the temperature of the reaction gas is lowered, the product is easy to deposit and the product adheres to respective members such as a valve member, a bellows and the like included in the poppet valve to lower an opening/closing accuracy of the valve. Therefore, in such a poppet valve, it is important that such a constitution is employed that deposition of product from the working fluid or adhesion thereof to the valve member and the like can be prevented.
For this reason, poppet valves with a heater which heats the interior of a casing, a valve member and the like by a heater to prevent adhesion of product have conventionally been proposed. In Japanese Patent No. 3005449 publication, there has been disclosed one where a band heater is wound on an outer face of a casing and a rod-shape heater is attached to a valve member for opening/closing a flow path through the interior of a hollow rod extending from the valve member. Also, in Japanese Patent No. 3012831, there has been disclosed one where a rubber heater is attached to an outer face of a casing and anther heater is attached an outer periphery of a cylindrical holding body integral with a valve member. Further, in JP-A 11-82807 publication, there has been disclosed one where a rubber heater is attached to an outer face of a casing and a flexible heater is housed in the interior of a hollow rod integral with a valve member.
However, in each of such conventional poppet valves, since a heater for heating a valve member is attached to the valve member or the rod which is a movable member, there is a problem that the weight of the entire movable member including the valve member or the rod is increased due to attachment of the heater so that a driving force required for opening/closing the valve must not only be increased correspondingly but also a response performance is deteriorated. In addition, since an impact generated for each of opening/closing operations of the valve member is directly transmitted to the heater, there is a drawback that the heater disconnects or breaks easily due to the impact. Also, since the valve member is always heated by the heater even when it is unnecessary to heat the valve member so strongly in a state where a large amount of working fluid is not flowing in the interior of the valve, there is a problem that a heat efficiency is poor and thermal deterioration of a rubber-made sealing member which is weak in heat occurs easily.
A technical object of the present invention is to provide a poppet valve with a heater which has an efficient and reasonable design structure and which has solved the above described conventional problems by employing such a constitution that a heater for heating a valve member is provided at a fixed position inside a valve casing without attaching the heater to the valve member, a rod or the like which is a movable member, thereby allowing transfer of much heat to the valve member as necessary.
According to the present invention for solving the above problem, there is provided a poppet valve with a heater, comprising: a valve casing which has a first main port and a second main port, a flow path connecting both the main ports to each other, and a valve seat provided inside the flow path; a cylinder which is coupled to the valve casing via a heat insulating portion; a valve member of a poppet type which is provided inside the valve casing to open/close the valve seat; a rod whose distal end portion is coupled to the valve member and whose proximal end portion extends into the interior of the cylinder via the heat insulating portion; a piston which is slidably disposed in the interior of the cylinder via a sealing member and is coupled to the proximal end of the rod; a heat transfer body which is disposed at a fixed position inside the valve casing along the rod and whose distal end portion is provided with a heat transfer face coming in contact with the valve member at a position of valve opening; first heater which is attached to the heat transfer body; and a second heater which is attached on an outer face of the valve casing.
According to the poppet valve of the present invention having the above constitution, since such a constitution is employed that the heat transfer body is provided at a fixed position inside the valve casing and the first heater for heating a valve member is attached to the heat transfer body so that the valve member comes in contact with the heat transfer body to be heated at a time of opening of the valve member, there does not occur such a problem that a driving force at a time of opening/closing is increased due to increase in weight of the valve member or a response performance is deteriorated like the case that the heater has been directly attached to the valve member or the rod. In addition, since such a system is employed that the valve member comes in contact with the heat transfer body to be directly heated at a time of valve opening when working fluid flows in the interior of the valve, an energy efficiency is high and the sealing member deterioration of the sealing member occurring in such a case that a direct heating is performed is hard to occur. Further, since an impact generated according to opening/closing of the valve member is not transferred to the heater, the problem of injury of the heater does not occur.
According to a specific embodiment of the present invention, the heat transfer body takes a cylindrical shape and it is disposed so as to surround the rod, and the heater is housed in the interior of the heat transfer body.
Also, the heat insulating portion is formed of a cylindrical heat insulating plate having a plurality of vent holes, and the heat insulating plate is provided between the valve casing and the cylinder concentrically with the rod.
According to a preferred embodiment of the present invention, the rod is partitioned to a first portion positioned on the side of the valve member and a second portion positioned on the side of the piston, and the second portion is formed of material having a heat transfer property lower than that of material of the first portion.
According to a specific embodiment of the present invention, a bellows is provided between a partition wall of an end portion of the valve casing and the valve member, and the heat transfer body is accommodated in the interior of the bellows and a heat receiving face coming in contact with a heat transfer face of the heat transfer body is formed at a portion of a back face of the valve member which is included in the bellows.